Telephone-exchange system.



C. L. GOODRUIVI. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY 23, 1915.

Patented; May 29, I917.

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new and useful CHARLES L. GOODRUM, OF NEW YORK, N. Y, ASSIGNDR, BY MESNE ASSIGNMENTS, T0

WESTERN ELECTRIC COMPANY, IN GORIPORATED, A

CORPORATION OF NEW YORK.

TELEPHQNE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Application filed July 23, 1915. Serial No. 41,478.

To all whom it may concern:

Be it known that 1, CHARLES L. GooDRUM, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems employing machine switchmg.

One of the features consists in vision of a circuit arrangement each line paths, one leading from second selectors the prowhereby connector may be set on a subscribers controlled by local automatic subscribers and the other from a toll operators position. When set by a local subscriber upon the wanted line, av test is made thereof, and if idle, the called partys bell is automatically rung in the ordinary manner. However, when the connector is set on the wanted line from the toll operators position over the other path, electromagnetic means is operated to apply ringing current to the called line, which will cause the bell thereof to give a signal difierent from the ordinary local signal. Thus the subscriber will be made aware of the nature of the call.

The called party in' responding to a toll call operates a relay at the connector to reverse the direction of the flow of current in the trunk leading back to the operators position, to operate a polarized relay thereat. This relay causes the extinguishment of the called supervisory lamp to indicate to the operator the response of the called party.

Inasmuch as toll calls are as a rule given preference over local calls, provision is made in the circuit arrangement of this invention to disable the test circuit of the connector when the same is set 'on the called line from the toll operators position. Thus the connector connects with the selected line terminating therein over either of two closes its 'ment magnet 17, conductors The brushes 73, 74 and 90 and terminals 72, 7 5, 89 only of the second selector are shown. The relay 10 is the stepping relay of the connector.

The invention will be more readily understood from a detailed description of the operation of the system. Assuming first that the connector is set over the trunk T. The stepping relay 10 is thereupon ener gized, and by opening its back contact removes ground from multiple test terminals 69 and 89 to render this connector busy to testing selectors. At its front contact it closes a'circuit for slow-acting relay 11 as follows: free pole of battery, relay 11, conductors 12 and 13, armature and front contact of relay 10 to ground. Relay 11 at its right armature and front contact presame from one position to the next upon 1ts deenergization in the well known manner: free pole of battery, magnet 17, conductor-'18, upper armature and front contact of relay 14, conductor 19, ground at the armature and back contact of relay 20. The cscapement magnet 17 at its right armature and front contact prepares a circuit for primary stepping magnet 21. As the sender S interrupts the line circuit a number of times, corresponding to the tens digit of the wanted line, each time the relay 10 front contact, the following circuit is closed for the primary stepping magnet 21 to step the connector to the group of contacts containing those of the wanted line, free pole of the battery, stepping magnet 21, conductor 22, side switch arm 23 and its first contact, conductor 24, right armature and front contact of escape- 25, l3, arma ture and front contact of stepping relay 10 to ground. The relays 11 and 14, being slow acting, do not release their armatures "ill during the line circuit interruptions. Upon the termination of tens selection the line circuit is closed at the sender g and the stepping relay 10 is consequently maintained energized. After an interval, the

slow acting relay 14, which is dependent for its continued energization upon a circuit leading through the back contact of the stepping relay 10, becomes deenergi'zed, and at its upper armature and front contact opens the circuit of the side switch escapement magnet 17, which, after a slight interval, denergizes and releases the side switch into the second position. In this position, the side switch arm 23 transfers the front contact of the stepping relay 10 from association with the primary magnet 21 and into association with the secondary magnet 26. Upon the first interruption of the line circuit by the sender S in the units selecting operation,-the armature 1O closes its back contact, whereupon the circuit previously traced for relay 14 is again closed.

This relay at its upper armature and front contact ,again closes the circuit of escapement magnet 17 previously traced. Each time the stepping relay is energized duringthe units selecting operation, the following circuit is closed to step the connector brushes 27, 28, 29 over the terminals 'of the selected group; freepole of the battery, magnet 26, conductor 33, side switch arm 23, conductor 24, rightv armature and front contact of magnet 17, conductors 25, 13, armature and front contact of stepping relay 10 to ground. Upon the termination of the units selecting operation, the stepping relay 10 is maintained energized and consequently the relay 14, after an interval, allows its armatures to fall back. The retraction of the upper armature opens, the circuit of the side switch escapement magnet 17, which is slow-acting and consequently holds up its armatures for an interval. A busy line is one whose multiple test terminal 32 is grounded. Consequently, if a ground is present on this test terminal, the following circuit is closed through the release magnet 34 of the connector before the slow magnet 17 can I deenergize and release the side switch: free pole of the battery, magnet 34, conductor 35, right armature and back contact of called supervisory relay 36, conductor 37, connector off-normal contact 38, conductor 87, lower armature and back contact of relay 14, conductor 77, right armature and back contact of relay 39, conductor 40, side switch arm 41 and its second contact, conductor 42, test brush 29 to grounded terminal 32. The connector is thereupon restored. The release magnet armature also restores the connector side switch in the well-known manner. The release magnet 34 at its left armature and front contact connects the busy back apparatus 86 to the line conductor 0;, thus informing the calling party that the line desired is busy, and at its right armature locks itself over the folmature and back contact of relay 20 to ground. When the calling party hangs up his receiver, this circuit is broken at the left armature and front'contaet of relay 11.

Assuming, however, that the line is idle when the connector brushes 27, 28 and 29 are connected to the terminals 30, 31 and-32, no ground is present upon the test terminal 32, and consequently the release magnet is not energized. The escapement magnet 17 in deenergizing, releases the side switch into position 3. In position 3, arm 41 grounds multiple test contacts 32 of the selected line by way of conductor 42 and brush 29, thus rendering this line busy to other testing connectors. In position 3 the following circuit is closed for the escapement magnet 17 to apply ringing current to the selected line: free pole of the battery,magnet 17 condue tor 18, conductor 43, side switch arm 44 and its third contact, conductor 45, left armature and front contact of relay 11, conductor 46, armature and back contact of relay 20 to ground. The escapement magnet 17 at its left armature and front contact closes the ringing circuit as follows: free pole of battery, interrupter 47, conductor 48, right armature and back contact of relay 39, conductor 49, marginal relay 20, conductor 50, leftarmature'and front contact of magnet 17, conductor 51,.arm 52 and its third contact, conductor 53, brush 28, terminal 31, line conductor 54, bell 55, condenser 56, return conductor 57, terminal 30, brush 27, conductor 58, arm 59 and its third contact, conductor 60, conductor 61, resistance 62 to ground. When the subscriber at substation B removes his receiver 79, the marginal relay 20 operates in the well-known manner, and by opening its back contact opens the circuit of the escapement magnet 17 which in de'einergizing, releases the side switch into the fourth position. The arms 59 and 52 of the side switch, in moving into position 4, close the following circuitv for the called supervisory relay 36: free pole of battery, left winding of relay 36, conductors 63, 64,

arm 52 and its fourth contact, conductor 53,

lift

naaaeoa 53;

over the circuit just traced and to the call-' mg party over the windings of relay 10.

cse circuits are separated conductively and joined inductively by the condensers Q C. en the parties finish their conversation and hang up their receivers, the following circuit is closed for the release magnet 34 of the connector: free pole of battery, magnet 34, conductor 35, right armature and back contact of relay 36, conductor 37, off-normal contact 38, conductor 68, left armature and backcontact of relay 11, conductor 46, armature and back contact of relay 20 to ground. The release magnet 34 of the connector in attracting its armature, restores the side switch in the wellown manner. lVhen the connector is completely restored, the release magnet is deenergized by the opening of off-normal contact 38. The retraction of the armature of stepping relay 10 again grounds test terminals 69, 89, thus rendering this connector mfectable to testing selectors.

Assuming now that the connector is seized by trunk T incoming from an operators position. The circuit of stepping relay 10 now leads as follows: free pole of battery, left winding of relay 10, conductor 70, conductor (Z, conductor 71, outer armature and back contact of relay 36, conductor a", terminal 72, brush 73, conductor 85, sender S at the operators position, and back over the return conductor 84, to brush 74, terminal 75, conductor d, relay 39, middle armature 81 and back contact of relay 36, conductors 76, a, 7 6, right winding of relay 10 to ground. This relay at its back contact removes ground from test terminals 69, 89 to render this connector unselectable to testing selectors, and at its front contact energizes the slow relay 11 as before. Relay 39 1S energized in series with relay 10. This relay, y attractingits left armature, opens the test circuit. Relay 11 prepares a circuit for slow relay 14. This circuit is closed upon the first retraction of the armature of stepping relay 10 as follows, when the sender S interrupts the line circuit during the tens selecting operation: free pole of battery, relay 14, conductor 15, right armature and front contact of relay 11, conductor 16, armature and back contact of relay 10 to ground. The relay 14 by attracting its upper armature, closes the following circuit for the escapement magnet 17 free pole of battery, magnet 17 conductor 18, upper armatureand front contact of relay 14, conductor 19, armature and back contact of relay 20 to ground. The escapement magnet 17 is thereupon energized. Each time the armature of relay 1O closes its front contact, the following circuit is closed for the primary magnet 21: free pole of the battery, magnet 21, conductor 22, arm 23 and its first contact, conductor 24, right armature Upon the first closure of the back contact of relay 10, slow relay 14 is energized as be fore. Each time the ste ping relay 10 closes its front contact, the Following circuit is closed for the secondary magnet 26: free pole of batter magnet 26, conductor 33, arm 23, conductor 24, right armature and front contact of magnet 17, conductor 25, conductor 13, armature and front contact of relay 10 to ground. At the end of units selection, the stepping relay 10 remains energized, and consequently the slow relay 14, after a slight interval, retracts its armatures. Although the release magnet is connected to conductor 77 by the retraction of the lower armature of magnet 14, as before, the circuit of release magnet 34 is not completed through to the test brush 29, due to the energized condition of the relay 39. Consequently, there is no circuit to energize the release magnet, even assuming the test terminal 32 of the selected line were grounded. When the circuit of escapement magnet 17 is opened at the upper armature and front contact of slow relay 14, this magnet after an interval retracts its armatures, thus releasing the side switch into position 3. In position 3, the arm 41 grounds the multiple terminals 32. As sume first that the called line is idle. In position 3 the escapement magnet 17 is energized over the following circuit: free pole of battery, magnet 17, conductors 18, 43, arm 44 and its third contact, conductor 45, left armature and front contact of relay 11, conductor 46, armature and back contact of relay 20 to ground. Magnet 17 at its left armature and front contact, closes the ringing circuit as follows: free pole of battery, interrupter 88, conductor 78, right .armature and front contact of relay 39, conductor 49, marginal relay 20, conductor 50, left armature and front contact of magnet 17 conductor 51, side switch 7 arm 52 and its third contact, conductor 53, brush 28, terminal 31, conductor 54, bell 55, condenser 56, conductor 57 ,terminal 30, brush 27, conductor 58, arm 59 and its third contact, conductor 60, conductor 61, resistance 62 to ground. It will be noted that the ringing circuit just traced is different from that previously traced in connection with a call incoming from an ordinary local subscriber. The bell 55, when rung over the circuit just traced, gives a signal different in character from that over the 011'- cuit previously traced in connection with a local 'call. Consequently, the subscriber will recognize this signal as a toll call and tracting its armatures, Hows the side switch to move to position 4 in the well known manner. In position 4 the following circuit is closed forthe called supervisory relay 36: free pole of the battery,

left winding of relay 36, conductors 63, 64, arm 52 and-its third contact, conductor 53, brush 28, terminal 31, conductor. 54, primary winding 64, transmitter 65, conductor 57, terminal 30, brush 27, conductor 58, arm 59, conductor a, 66, relay 36, conductor 67, conductor 61, resistance 62 to ground. The relay 36 by attracting its armatures 80, 81, reverses the direction of the flow of current back to the operators position. This reversal of current may operate a polarized relay thereat to extinguish the supervisory lamp of the called party in the cord circuit. This circuit is as follows: free pole of bat tery, left winding of relay 10, conductors 70, d, 71, 82, armature 81 and its front contact, conductor (1', side switch arm 83 and its fourth contact, terminal 75, brush 74, conductor 84, return conductor 85, brush 73, terminal 72, conductor a, armature 80 andvits front contact, conductors 76, a, 76', right winding of relay 10 to ground. It will be noted that in the fourth position of the side switch, arm 83 short-circuits the relay 39, thus removing its impedance from the talking circuit.

Whenthe circuit of conductors 85, 84 is broken upon the termination of the call, the stepping relay 10 becomes deenergized, and in turn deenergizes slow relay 11. Assuming that the called party at substation B has already hung up hls receiver, the following circuit is closed for the release magnet 34 of the connector: free pole of battery, magnet 34, conductor 35, right armature and back contact of relay- 36, conductor 37, oilnormal contact 38, conductor 68, left armature and back contact of relay 11, conductor 46, armature and back contact of relay 20 to ground. The relay 34 in attracting its armature, restores the side switch in the well-known manner. When the connector is completely restored, the opening of oil-normal contact 38 deenergizes the release magnet 34.

If the selected line is busy when the connector is set thereon over the trunk T, the

memos side switch moves into position 3, as de-' scribed. In this position, the escapement magnet 17 is energized over the circuit traced, leading through the side switch arm 44, left armature and front contact of slow relay 11, and armature and back contact of marginal relay 20, but due to the simultaneous closure of a circuit for the marginal relay 20, including the called substation telephonic apparatus, the escapement magnet 17 is immediately denergized due to the associated with each line, an automatic switch wherein said lines terminate, and means for causing said switch to select a line, of means automatically operated by the setting of the switch on one of said lines for operating the signal thereof variably.

2. In a telephone exchange system, the

combination with subscribers lines, a signal associated with each of said lines, a connector wherein said lines terminate, and selectors, of two trunks terminating at one end in said connector and at the other in different selectors, means for setting said connector on said lines over either trunk, and means at said connector automatically operated incident to setting said connector on the called line over one of said trunks to operate said signal in one manner, and automatically operated incident to setting said connector on said called line over the other trunk to operate said signal in a diiferent manner.

3. In a telephone exchange system, the combination with subscribers lines, a signal associated with each of said lines and a connector wherein said lines terminate, of two trunks terminating at one end in said connector and at the other in different selectors, a source of current connected to said trunks at said connector, means for setting said connector on the called line over either trunk, automatic means at said connector for variably operating the called line signal according to the trunk over which the connector is set, andmeans at said connector for reversing the direction of the flow of current from said source when said connector is set over one of said trunks for signaling over the connected trunk.

4. In a telephone exchange system, the combination with subscribers lines and a connector wherein said lines terminate, of two trunks terminating in one end in said connector and at the other end in diiierent selectors, means for setting said connector on said lines over either trunk, a test circuit associated with said connector, and a relay at said connector adapted to be automatically operated if the connector is set over one of said trunks to render said test circuit inoperative.

5. In a telephone exchange system, the combination with subscribers lines, a signal associated With each line and a connector wherein said lines terminate, of two trunks terminating at one end in said connector and at the other end in different selectors, means for setting said connector on said lines over either trunk, a test circuit associated with said connector, a relay at said connector adapted to be operated when the connector is set over one of said trunks to render said test circuit inoperative, and sources of signaling current of difi'erent character controlled by said relay.

In Witness whereof I hereunto subscribe my name this 21st day of July, A. D. 1915. CHARLES L. GOODRUM. 

